What's starting to annoy me more and more with my SP4, is that I have constant issues with Bluetooth! Again and again the bluetooth settings and/or driver seem "half-dead". I typically notice this first, when either the mouse (surface mouse) or the pen is not working. If I then bring up the settings, the bluetooth square is light-blue, i.e. enabled, but when I click it, nothing happens, i.e. it does not switch off but remains light blue. At this point I know, it's not even enough to reboot, I have to shutdown (i.e. power down) the system, wait a few seconds and only then I can restart again and then I have a chance that BT is working again. Looks like a major driver issue to me. For a device so advanced and expensive that is a real shame!